Dicamba: U. of Arkansas Posts Second Response To Monsanto’s Petition

    Soybeans at mid-season after early dicamba drift injury. ©Debra L Ferguson Stock Photography

    Editor’s Note: The University of Arkansas has distributed a second response to a petition filed by Monsanto with the Arkansas Plant Board. Click here to view the petition and related information from Monsanto. We are posting the university’s release below.

    University of Arkansas System Division of Agriculture’s rebuttal to key points made in Monsanto’s petition to the Arkansas State Plant Board:

    Number 1: Monsanto claim: “Importantly, Dr. Norsworthy’s assumption that 5% visual damage results in significant yield loss is unfounded and contradicted by other field studies.” Norsworthy was referring to symptomology only. As we have found, yield loss will be determined by multiple factors: Growth stage of the plant, rate of dicamba exposure, number of times the plant has come into contact with dicamba and environmental conditions following exposure.

    Number 2: Monsanto claims: “… weed scientists who investigated reports of dicamba symptomology in the eight affected counties predicted that the mild symptomology that was reported there is unlikely to produce much yield reduction … .” This claim cites comments made early in the growing season as both researchers and growers worked to understand the effects they were seeing in the fields and before some fields were hit multiple times with off-target herbicide. What is perceived at the beginning of the season and what’s observed at the end of the season are not the same.

    Number 3: Monsanto claim: “Dr. Norsworthy told the task force that the symptomology observed in the studies he conducted was all attributed to volatility.” What he actually told the task force: “Based on what I’ve seen is, I believe the majority of it is volatility … based back on the data.” View video from time mark 1:14:33 at Where 100 percent symptomology occurs, it’s likely to be volatility based on data from our plots at the Northeast Research and Extension Center in Keiser, Arkansas.

    Number 4: Monsanto claim: “The proposed ban is arbitrary because it is based on unsubstantiated theories regarding product volatility that are contradicted by science.” There have been 11 field studies conducted by six weed scientists in various parts of the country that point to the chemistry’s volatility. While there were similarities between field studies, there are significant differences in the results in vapor chamber or humidome trials versus those conducted in the field.

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    Number 5: Monsanto claim: “These results suggest that additional applicator training on the use of these new low-volatility dicamba formulations will significantly reduce instances of off-target movement in 2018.” The University of Arkansas System Division of Agriculture offered many opportunities to learn application technology: More than 770 applicators going through our face-to-face spray clinics in 2016-17, and 1,074 applicators took the mandatory online training specifically designed for application of Engenia, the only dicamba product approved for in-crop use. Additional trainings were offered by BASF and Dennis Gardisser of WRK of Arkansas. However, training cannot correct off-target damage caused by volatility and dust. Volatility can be influenced by a number of factors including herbicide chemistry, soil and air temperature, the number of acres treated, and the amount of canopy coverage, and tank-mix partners, among other things.

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